I have (or rather my friend has, but I'm retelling it...) an excellent story to illustrate the effect of equal first ranks.
My friend (lets call her...1) ranked equal first with another friend (for convenience, lets call her 2) at school in studies of religion. If 1 sat the exam and got an exam mark of 94 while the 2 got 92, friend 1 would get an exam mark of 94 and an assessment mark of 93...so it would disadvantage her.
However, my friend was unfortunately *sick* and missed her studies of religion final exam, and thus went in with a first ranking. Another friend (who was ranked 4th i think...) topped the class in the exam with a mark of 94. Since there could be no average between the 2 top marks, both friend 1 and friend 2 were allocated 94 as an assessment mark. Friend 2 got her real mark for her exam, but since friend 1 didn't write the exam, she got that assessment mark for her exam as well....and as a result ended up coming 7th in the state for SOR!!!
Edit: i'm not advocating feigning ill for ur exams...